1. Field of the Invention
This invention relates broadly to methods and apparatus for determining position of and/or for positioning an object relative to both (a) its distance to a surface and (b) the orientation of its longitudinal axis to such surface. More particularly, it concerns such methods and apparatus especially suited for accurately positioning cameras, video recorders, or other objects relative to surfaces in a submarine location.
2. Description of the Prior Art
There are many situations in which the location of an object relative to both (a) its distance to another object or to a surface and (b) its orientation to such object or surface must be determined in order to (1) accurately position the object relative to the surface, (2) to project something from the object to the surface or other object and (3) for many other reasons. This invention is specifically directed to methods and apparatus useful in those particular situations in which an object, e.g., a camera, a recording system, an imaging device, analysis instrument, etc., must be accurately positioned relative to a surface under conditions that present acute problems in determining the distance and orientation of the object relative to the surface, particularly in submarine locations. However, it is contemplated that these methods and apparatus will be put to other uses than in submarine environments.
A great number of underwater visual recordings are made with photographic or video cameras which have limited remote controls. This is particularly true of deep-sea camera systems where camera lens opening and focus are preset and the photographer must somehow arrange for the subject to be at the correct distance, within the field of view and properly oriented with respect to the viewing system at the time of exposure.
One approach is providing better control in submarine photography would be to incorporate the ranging features of advanced, above the surface cameras. Such cameras use a variety of techniques to obtain proper exposure conditions for control. The most common is a triangulation arrangement which superimposes the images received by a pair of space optical receivers and provides automatic, mechanical adjustment of the lens until the received images are coincident. Microelectronics are used to perform the image comparison and thereby provide automatic focusing (see U.S. No. 4,435,744 and 4,313,654).
Other advanced surface cameras use microprocessor based optical-image analyzers to determine correct focus. Also, sonar systems are used in some cameras.
The optical systems of the surface cameras generally use infrared light beams with reflected light intensity, image analysis and triangulation. Unfortunately, the devices and techniques developed for surface cameras are not directly transferable to submarine camera systems. Differences, between the physical properties of air and water result in major differences in the propagation of light and sound in the two media. Additionally, spurious material and signals can cause may "false" exposures to occur with submarine photography while this is not a serious consideration in use of surface cameras. Therefore, a camera system which depends on the propagation of energy waves for operation must be designed for the medium in which it is to be used.
Extensive development work has occurred relative to submarine photography, e.g., see "Underwater Photography--Scientific and Engineering Applications", compiled by Paul Ferris Smith, Van Nostrand Reinhold Company, 422 p., 1984. Such work has included use of (a) optical triggering of underwater cameras, e.g., see U.S. No. 3,446,555 and pp. 223-228, "Deep Sea Photography", J. B. Hersey, Editor, The Johns Hopkins Press, 1967, and (b) sonar techniques, e.g., see U.S. No. 4,105,990; 4,335,944; 4,381,144, 4,447,896 and copending U.S. patent application Ser. No. 842,139, now U.S. Pat. No. 4,707,094, filed Mar. 21, 1986.
Nothwitstanding the extensive prior work and developments with surface and submarine camera systems, substantial improvements are needed for the submarine systems.